In certain tire retreading operations, molded and cured tread strips are attached to the buffed tire casing with a cushion gum layer. The assembled casing and new tread are placed in a pressure and heat controlled chamber (autoclave) to cure the cushion gum layer bonding the tread to the casing. To ensure the uniform application of pressure and heat to the assembly, each assembled tire is first placed in an envelope. The envelope is a toroid-shaped bag that encloses the outer surface of the tire and is evacuated before the tire is placed in the chamber. The envelope provides a uniform surface for transmitting pressure and heat effectively to the outer surface of the tire. Envelopes are made of elastomeric sheet material and are typically elasticized to help conform to the outer surface of the tire. To place a tire casing and tread assembly in an envelope, the envelope must be spread and held open sufficiently wide to accept the assembly.
Envelope spreader machines are available commercially, for example, the "Enveloper" available from Matteuzzi USA, Colonial Heights, Va., the "Envelope Spreader" from TRM srl, Italy, and the "Olson Envelope Expander" from Olson Equipment Co., Mt. Pleasant, Mich. These machines include several, typically eight, articulated arms that rotate to spread open the envelope. The articulated arms include a major or swing arm mounted for pivoting on a frame and driven by a pneumatic drive system, and a second arm pivotally fastened to the swing arms and having a hook or jaw member at a free end to engage the edge of the envelope. The hooks hold the envelope edge in a relative circular orientation so that pivoting of the swing arms with follower movement of the second arms spreads the edges to form an opening for the tire.
An envelope spreader machine must typically accommodate tires ranging from light truck sizes to large long haul double width tires. Because conventional spreaders move the arms between two fixed positions, adjustments for tire size are made by changing the length the hook member extends from the swing arm. The hooks typically have shanks with two or three mounting holes and are bolted to the arm joint. Even with a power driven wrench, removing and reinstalling the bolts to change the hook position takes several minutes for each arm.
The present invention overcomes the deficiencies in the art with a quick adjusting hook member that allows the hook and swing arm adjustment to be made quickly and easily.
According to a preferred embodiment of the invention, a spreader arm is mounted to the swing arm of a spreader at a fixed point. The spreader arm has a plurality of adjusting holes spaced along its length. A sleeve or collar is slidably mounted on the spreader arm and includes a positioning hole with a removable pin to engage one of the adjusting holes. A jaw for engaging the envelope is fastened at the end of the sleeve.
According to an alternative embodiment, the sleeve is attached to the swing arm for pivoting movement and the arm is slidably inserted in the sleeve.
The sleeve and pin can be positioned at any of the adjustment holes to provide the desired length relationship with the swing arm. In addition, the pin is a quick release spring ball pin for fast removal and insertion in the adjustment holes.
The sleeve securely engages the spreader arm to prevent unwanted movement of the jaw relative to the spreader arm, both for operator safety and reliable functioning of the spreader machine.